Morphological feature

When the structural features of crystalline polymers are examined beyond the level of the unit cell, it is very important that their semi-crystalline character 

5 Wide-angle x-ray pattern of noncrystalUne natural rubber, (Courtesy of A, F. 

Different kinds of preferred orientations can also be developed with crystalline polymers. The native state of many macromolecules of biological interest, such as the fibrous proteins, is characterized by a preferred crystalline orientation. Similar conditions can also be obtained in other polymers by deformation of the specimen 

There is substantial evidence to indicate, at all the levels of morphology that are amenable to study, well-defined organized structures exist. Small-angle x-ray studies indicate structures having linear dimensions that correspond to hundreds of angstroms.(34,35) A typical low-angle x-ray pattern from a highly axially oriented 

Typical electron microscope studies of homopolymers crystallized from the pure melt are shown in Figs. 1.10 and 1.11 respectively.(37,38) Lamellar-like crystallites are the characteristic habit. Detailed studies indicate that the thickness of the lamellae is usually the order of several hundred angstroms, depending on the crystallization conditions. Lateral dimensions on the other hand are the order of a micrometer. 

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Resistance to antimicrobial agents is of concern as it is well known that bacterial resistance to antibiotics can develop. Many bacteria already derive some nonspecific resistance to biocides through morphological features such as thek cell wall. Bacterial populations present as part of a biofilm have achieved additional resistance owkig to the more complex and thicker nature of the biofilm. A system contaminated with a biofilm population can requke several orders of magnitude more chlorine to achieve control than unassociated bacteria of the same species. A second type of resistance is attributed to chemical deactivation of the biocide. This deactivation resistance to the strong oxidising biocides probably will not occur (27). 

Mechanical properties of mbber-modifted epoxy resins depend on the extent of mbber-phase separation and on the morphological features of the mbber phase. Dissolved mbber causes plastic deformation and necking at low strains, but does not result in impact toughening. The presence of mbber particles is a necessary but not sufficient condition for achieving impact resistance. Optimum properties are obtained with materials comprising both dissolved and phase-separated mbber (305). 

The outstanding morphological feature of these rubbers arises from the natural tendency of two polymer species to separate one from another, even when they have similar solubility parameters. In this case, however, this is restrained because the blocks are covalently linked to each other. In a typical commercial triblock the styrene content is about 30% of the total, giving relative block sizes of 14 72 14. At this level the styrene end blocks tend to congregate into spherical or rod-like glassy domains embedded in an amorphous rubbery matrix. These domains have diameters of about 30 nm. 

The purpose of our study was to model the steady-state (capillary) flow behavior of TP-TLCP blends by a generalized mathematical function based on some of the shear-induced morphological features. Our attention was primarily confined to incompatible systems. 

The microphase structure was clearly observed in transmission electron micrographs of the film of amphiphilic copolymers cast from aqueous solutions [29, 31]. An important finding was that no microphase structure was observed for the film cast from organic solutions. This difference indicates that a microphase structure is formed in aqueous solution, but not in organic solution. Different hydrophobic groups showed considerably different morphological features i.e. whether microphase separation leads to a secondary or higher structure depends on the type of hydrophobic units in the copolymers [31],... 

When a polymer film is exposed to a gas or vapour at one side and to vacuum or low pressure at the other, the mechanism generally accepted for the penetrant transport is an activated solution-diffusion model. The gas dissolved in the film surface diffuses through the film by a series of activated steps and evaporates at the lower pressure side. It is clear that both solubility and diffusivity are involved and that the polymer molecular and morphological features will affect the penetrant transport behaviour. Some of the chemical and morphological modification that have been observed for some epoxy-water systems to induce changes of the solubility and diffusivity will be briefly reviewed. 

Annexin V PT UOS staining is another procedure which allows to label the cells by allowing the observation of the morphological features of apoptosis. 

Morphological features for POPs can range from low-temperature elastomers (when aliphatic alkoxy substituents of different length are attached to the polyphosphazene skeleton), to crystalline, film- and fibre-forming materials... 

The various morphological features of barites from the Kuroko and Mariana deposits, when combined with the experimental studies on barite precipitation, suggest that the surface reaction mechanism was dominant for the formation of these barites. This implies that the concentration product, m 2+) msol-), at the initiation of barite precipitation was probably less than ca. 100 times that for equilibrium. 

Solvent-cast films of tyrosine-derived polyiminocarbonates and polycarbonates were virtually indistinguishable in appearance and exhibited similar morphological features. When examined by X-ray diffraction, using an automated Scintag Pad V diffractometer all tested films were found to be completely amorphous. The lack of ordered domains in solvent-cast films seemed to be a general feature of tyrosine-derived polyiminocarbonates and polycarbonates, irrespective of the pendent chain configuration of the monomeric dipeptide. 

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